In the petroleum products, lubricating oils, for example, are the products with the importance weighed on the flowability at a low temperature. For this reason, a base oil used for these products desirably has a wax component such as a normal paraffin, or the like, which causes the aggravation of the low temperature flowability, being completely or partially removed, or converted to a different component from a wax component.
A known dewaxing technique for removing a wax component from a hydrocarbon oil is, for example, a method in which a wax component is extracted using a solvent such as liquid propane, MEK, or the like. However, this method poses a problem of high operating costs.
On the other hand, a known dewaxing technique for converting a wax component in a hydrocarbon oil to a non-wax component is, for example, an isomerization dewaxing in which a hydrocarbon oil is, in the presence of hydrogen, allowed to contact a hydroisomerization dewaxing catalyst having dual functions of hydrogenation-dehydration ability and isomerization ability to isomerize a normal paraffin in the hydrocarbon oil to an isoparaffin (e.g., Patent Literature 1).